THE EFFECTS OF VACCINATION IN PREGNANCY ON THE FOETUS

Safety of Administering Live Vaccines During Pregnancy: A Systematic Review and Meta-Analysis of Pregnancy Outcomes

Live-attenuated vaccines (LAV) are currently contraindicated during pregnancy, given uncertain safety records for the mother-infant pair. LAV might, however, play an important role to protect them against serious emerging diseases, such as Ebola and Lassa fever. For this systematic review we searched relevant databases to identify studies published up to November 2019. Controlled observational studies reporting pregnancy outcomes after maternal immunization with LAV were included. The ROBINS-I tool was used to assess risk of bias. Pooled odds ratios (OR) were obtained under a random-effects model. Of 2831 studies identified, fifteen fulfilled inclusion criteria. Smallpox, rubella, poliovirus, yellow fever and dengue vaccines were assessed in these studies. No association was found between vaccination and miscarriage (OR 0.98, 95% CI 0.87-1.10), stillbirth (OR 1.04, 95% CI 0.74-1.48), malformations (OR 1.09, 95% CI 0.98-1.21), prematurity (OR 0.99, 95% CI 0.90-1.08) or neonatal death (OR 1.06, 95% CI 0.68-1.65) overall. However, increased odds of malformations (OR 1.24; 95% CI 1.03-1.49) and miscarriage after first trimester immunization (OR 4.82; 95% CI 2.38-9.77) was found for smallpox vaccine. Thus, we did not find evidence of harm related to LAV other than smallpox with regards to pregnancy outcomes, but quality of evidence was very low. Overall risks appear to be small and have to be balanced against potential benefits for the mother-infant pair.

Risks Associated With Smallpox Vaccination in Pregnancy: A Systematic Review and Meta-analysis

OBJECTIVE

To estimate the maternal and fetal risks of smallpox vaccination during pregnancy.

DATA SOURCES

MEDLINE, Web of Science, EMBASE, Global Health, ClinicalTrials.gov, and CINHAL from inception to September 2014.

METHODS OF STUDY SELECTION

We included published articles containing primary data regarding smallpox vaccination during pregnancy that reported maternal or fetal outcomes (spontaneous abortion, congenital defect, stillbirth, preterm birth, or fetal vaccinia).

TABULATIONS, INTEGRATION, AND RESULTS

The primary search yielded 887 articles. After hand-searching, 37 articles were included: 18 articles with fetal outcome data and 19 case reports of fetal vaccinia. Outcomes of smallpox vaccination in 12,201 pregnant women were included. Smallpox vaccination was not associated with an increased risk of spontaneous abortion (pooled relative risk [RR] 1.03, confidence interval [CI] 0.76-1.41), stillbirth (pooled RR 1.03, CI 0.75-1.40), or preterm birth (pooled RR 0.84, CI 0.62-1.15). When vaccination in any trimester was considered, smallpox vaccination was not associated with an increased risk of congenital defects (pooled RR 1.25, CI 0.99-1.56); however, first-trimester exposure was associated with an increased risk of congenital defects (2.4% compared with 1.5%, pooled RR 1.34, CI 1.02-1.77). No cases of fetal vaccinia were reported in the studies examining fetal outcomes; 21 cases of fetal vaccinia were identified in the literature, of which three neonates survived.

CONCLUSION

The overall risk associated with maternal smallpox vaccination appears low. No association between smallpox vaccination and spontaneous abortion, preterm birth, or stillbirth was identified. First-trimester vaccination was associated with a small increase in congenital defects, but the effect size was small and based on limited data. Fetal vaccinia appears to be a rare consequence of maternal smallpox vaccination but is associated with a high rate of fetal loss.

Medical management of vulnerable populations and co-morbid conditions of victims of bioterrorism

Planning for the medical response to bioterrorism has primarily focused around the needs of the population as a whole. There has been little discussion pertaining to certain vulnerable groups such as children, pregnant women, or immunocompromised patients, yet they will likely comprise a significant subset of the exposed population. In addition, they will be at increased risk for morbidity and mortality following an attack. The emergency response to bioterrorism will be more complex as it relates to these vulnerable populations. Careful consideration of their special needs, some of which are presented in this article, may refine our efforts.

Relation between smallpox vaccination and outcome of pregnancy

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